Is there a darkmode setting for HN?

I use a hacked together custom style sheet:

  a:link{
   color: lightgray;
  }

  #hnmain {
   background-color: #202020;
  }

  body {
   background-color: black;
  }

  .pagetop a:visited {
   color: #707070;
  }

  .c00, .c00 a:link {
   color: lightgray;
  }

In FF I use CSS override. Perhaps there are other plugins. For hn.algolia.com you might need another.

It respects a global dark mode setting in the browser and looks fine. I'm using Bromite with dark mode. I see a sort of Halloween theme. Black background, white text, orange banner.

No, but there's lots of browser extensions that can do it.

It inverts quite well with e.g. darkreader or noir